Prostate diseases are a major problem for aging men. Prostate cancer is the most commonly diagnosed cancer and the second leading cause of cancer deaths in U.S. men. Furthermore, benign prostate hypertrophy (BPH) affects most men by age 80. The Baltimore Longitudinal Study of Aging (BLSA)is defining anatomic and physiologic characteristics that distinguish normal prostate growth with age and the development of prostate disease; identifying hormonal changes important in the diseases; and characterizing markers(serum and genetic) that could identify high risk groups, and increasing knowledge regarding the development and progression of prostate disease, and lead to methods of disease prevention. The BLSA prostate study pioneered the use of prostate specific antigen (PSA) velocity to improve the specificity of PSA. testing. Less than 5% of men without prostate cancer have a rate of change in PSA exceeding 0.75ng/ml per year; while 70% of men with cancer have a rate of change in PSA that exceeds 0.75ng/ml per year. These data have now been confirmed in large prospective screening trials. The BLSA has recently analyzed free PSA levels using frozen sera from men with and without prostate cancer. Free PSA levels were significantly lower in cancer cases 10 years before diagnosis; while total PSA levels were significantly different 4 years before diagnosis. This finding could have important implications regarding early detection of prostate cancer. Human studies of androgen levels in men with and without prostate cancer have reported varying results. A preliminary case-control analysis in BLSA men with and without prostate cancer, found no significant differences in total and free testosterone levels at 0-5, 5-10, and 10-15 years before diagnosis of disease.